init

The init process (from initiate ) is the first process in the system in Unix systems : It usually has the process ID 1. It traditionally starts all other processes; How it does this is specified in the file under System-V -oriented systems such as Solaris ( SysVinit ), and in the file under the BSDs . /etc/inittab/etc/ttys

Linux -based operating systems (the init process is not part of the Linux kernel) traditionally use also the System V - daemon , since 2011 the now widespread distribution began systemd to replace the System V daemon.

On Mac OS X it was replaced by launchd .

On today's systems, the kernel also starts other internal processes, so the statement primarily applies to user processes.

Ending the init process with the kill command ( kill -9) is equivalent to shutting down the system. If you want to change the configuration effectively during operation, the following must be entered after changing the configuration file:

kill -1 1

In the System V-oriented operating systems, the init process manages the various run levels ; The BSDs, on the other hand, traditionally only know two modes, single-user and multi-user .

Since starting processes with the help of init on today's systems, with hardware changing during operation, is no longer entirely up-to-date, there are attempts to introduce alternatives. Examples are InitNG , eINIT , Upstart from Ubuntu , Launchd in Mac OS X and systemd in Fedora . Systemd is now also used in Debian and Ubuntu, where it replaces SysVinit and Upstart, which means that Systemd is used in the most widespread Linux distributions.

Examples of init systems

Asynchronous: systemd  | Upstart  | InitNG  | launchd  | cinit  | runit  | Minit  | Jinit | UNIT | s6 | SMF  | sinit | GNU shepherd

Synchronous: SysVinit | OpenRC

Web links

• Comparison of several init systems

Individual evidence

1. ^ Fedora Project: Feature List. fedoraproject.org, accessed February 15, 2012 .